There are a lot of different books that have very disappointing endings, but one book in particular that is known for having a poorly written ending is "The Catcher in the Rye" by J.D. Salinger. The book is about a teenager named Holden Caulfield who is struggling to deal with the death of his brother and the phoniness of the world around him. Holden is eventually committed to a mental institution, and the book ends with him saying goodbye to his family and leaving to go live with his aunt in California.
While many people believe that the ending of the book is a fitting conclusion to Holden's story, others find it to be very abrupt and poorly written. There are a lot of loose ends that are never resolved, and many readers feel like they are left hanging. It is definitely one of the most disappointing endings to a book, especially considering how well the rest of the story is written.